Skadden, Arps, Slate, Meagher & Flom and Wachtell, Lipton, Rosen & Katz have taken the lead roles in Yahoo Inc.’s $7.1 billion sale of a 20 percent stake in Alibaba Group Holding Ltd., the Chinese Internet company.

Hangzhou-based Alibaba will buy back the shares, which represent half of Yahoo’s stake in the Chinese company. The deal is the largest e-commerce mergers and acquisition deal ever.